<!doctype html>
<title>CSS Selectors: :is() and :where() parsing</title>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="help" href="https://drafts.csswg.org/selectors-4/#matches">
<link rel="help" href="https://drafts.csswg.org/selectors-4/#zero-matches">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style id="test-sheet">
  random-selector { color: blue; }
</style>
<script>
  let rule = document.getElementById("test-sheet").sheet.cssRules[0];
  function assert_valid(expected_valid, pattern, description) {
    test(function() {
      for (let pseudo of ["is", "where"]) {
        let selector = pattern.replace("{}", ":" + pseudo)
        rule.selectorText = "random-selector";
        rule.selectorText = selector;
        (expected_valid ? assert_equals : assert_not_equals)(
          rule.selectorText,
          selector,
          `${description}: ${selector}`
        );
      }
    }, description);
  }

  assert_valid(true, "{}(div + bar, div ~ .baz)", "Multiple selectors with combinators");

  assert_valid(true, "{}(:is(div))", "Nested :is");
  assert_valid(true, "{}(:where(div))", "Nested :where");

  assert_valid(true, ":host({}(div))", "Nested inside :host, without combinators");
  // See https://github.com/w3c/csswg-drafts/issues/5093
  assert_valid(false, ":host({}(div .foo))", "Nested inside :host, with combinators");

  assert_valid(true, "{}(:hover, :active)", "Pseudo-classes inside");
  assert_valid(true, "{}(div):hover", "Pseudo-classes after");
  assert_valid(true, "{}(div)::before", "Pseudo-elements after");
  assert_valid(false, "{}(::before)", "Pseudo-elements inside");

  assert_valid(true, "{}(div) + bar", "Combinators after");
  assert_valid(true, "::part(foo):is(:hover)", "After part with simple pseudo-class");
  assert_valid(false, "::part(foo):is([attr='value'])", "After part with invalid selector after");

  assert_valid(true, ":not({}(div))", "Nested inside :not, without combinators");
  assert_valid(true, ":not({}(div .foo))", "Nested inside :not, with combinators");
</script>
